HighestRandomWeightHash<TKey, TBucket>

Namespace: SnowBank.IO.Hashing · class

Uses the the Highest Random Weight Hashing strategy (HRW, also called Rendezvous Hashing) to deterministically choose a TBucket for any TKey

Constructors

HighestRandomWeightHash<TKey, TBucket>

HighestRandomWeightHash<TKey, TBucket>(IEnumerable<(TBucket, ulong, double)> buckets, Func<ulong, TKey, ulong> kf)

Create a HRW Hasher using a list of weighted Buckets (with already computed Seed)

HighestRandomWeightHash<TKey, TBucket>(IEnumerable<TBucket> buckets, Func<ulong, TKey, ulong> kf, Func<TBucket, ulong> nf, ulong seed = 0)

Create a HRW Hasher using a list of Buckets

All nodes will use weight = 1.0

HighestRandomWeightHash<TKey, TBucket>(IEnumerable<(TBucket, double)> buckets, Func<ulong, TKey, ulong> kf, Func<TBucket, ulong> nf, ulong seed = 0)

Create a HRW Hasher using a list of weighted Buckets

Properties

Count

int Count { get; }

Return the number of buckets available

HashFunction

Func<ulong, TKey, ulong> HashFunction { get; }

Hash function used to compute the score

HF(BUCKET_SEED, KEY) => 0..ulong.MaxValue

Methods

Choose

TBucket Choose(TKey key)

Choose the best bucket for the given key

Returns: Bucket with the highest score for this key

ChooseMultiple

TBucket[] ChooseMultiple(TKey key, int n)

Choose the first n server responsible for a given key, in descending priority

• n — Number of servers to select (>= 1)

Returns: Array of length up to n with the first server, then the second and so on. If n is larger than the number of buckets, then all the buckets will be returned.

(key, 1) is equivalent to calling (key), and (key, Buckets.Count) is equivalent to calling (key).ToArray()

RankBy

IEnumerable<TBucket> RankBy(TKey key)

Rank all buckets for a key, from the highest score to the lowest score

Returns the list of all buckets from the highest to the lowest

Top 3 server: List topThree = hrw.RankBy(KEY).Take(3).ToList();

Secondary server:BUCKET secondary = hrw.RankBy(KEY).Skip(1).FirstOrDefault();

Score

IEnumerable<(TBucket, double)> Score(TKey key)

Compute and return the score of all buckets for a given key

Returns: Unordered list of (Bucket, Score) for this key